Method for producing post-treated carbon black

ABSTRACT

The invention concerns a method for producing post-treated carbon black, where the carbon black is fluidized in the fluidized bed while adding fluidizing agents and brought into contact with a post-treatment agent.

[0001] The invention concerns a method for producing post-treated carbonblack.

[0002] Carbon black is chiefly used as black pigment in paints andprinting inks because of its excellent properties. There is a largeselection of pigment blacks with various properties available. Variousmethods are used to produce pigment black. The most common is productionby oxidative pyrolysis of carbon-containing carbon black raw materials.Here the carbon black raw materials are incompletely combusted at hightemperatures in the present of oxygen. This class of carbon blackproduction processes includes, for example, the furnace black process,the gas black process and the flame black process. Chiefly polynucleararomatic carbon black oils are used as carbon-containing raw materialsfor carbon blacks.

[0003] The surface chemistry of carbon blacks is dependent on theproduction process that is selected. With the furnace black process,carbon black formation takes place in a highly reducing atmosphere,while with the gas black process, atmospheric oxygen has free access tothe carbon black formation zone. Accordingly, the gas blacks have aconsiderably higher content of surface oxides immediately afterproduction than do furnace blacks.

[0004] Pigment blacks can be oxidatively post-treated in order toincrease their content of volatile components. Nitric acid, nitrogendioxide and, to a lesser extent, even ozone are used as oxidationagents. The oxidation process in this case is decisively dependent onthe carbon black production process. Oxidation of furnace blacks withnitric acid is known from U.S. Pat. No. 3,565,657.

[0005] Oxidizing furnace blacks by ozone treatment is also known (U.S.Pat. No. 3,245,820, U.S. Pat. No. 3,364,048, U.S. Pat. No. 3,495,999).Disadvantages of the known processes are the poor mass and energytransfer, poor homogeneity of the product, equipment parts that aremechanically in motion, and a discontinuous mode of operation.

[0006] The task of the invention is to make available a method in whichoptimum mass and energy transfer takes place, the product has very goodhomogeneity, and the process can be operated continuously.

[0007] The object of the invention is a method for producingpost-treated carbon black, characterized by the fact that the carbonblack is fluidized in a fluidized bed while adding fluidizing agents andbrought into contact with a post-treatment agent.

[0008] As carbon black, one may use furnace black, gas black, channelblack, flame black, thermal black, acetylene black, plasma black,inversion blacks which are known from DE 195 21 565, Si-containingblacks which are known from WO 98/45361 or DE 19613796, ormetal-containing blacks which are known from WO 98/42778, arc black andblacks that are by-products of chemical production processes. The carbonblack can be modified by the presented reactions.

[0009] Carbon blacks that are used as reinforcing filler in rubbermixtures can be used.

[0010] Color blacks can be used.

[0011] Other blacks can be: conductive black, carbon black for UVstabilization, carbon black as filler in systems other than rubber, forexample, in bitumen and plastic, carbon black as reducing agent inmetallurgy.

[0012] Preferably a furnace black can be used as the carbon black.Normally and more highly structurized furnace blacks with a DBP valuegreater than 70 mL/100 g, preferably greater than 90 mL/100 g, areespecially preferably used.

[0013] Carbon black mixtures can also be used as the carbon black.

[0014] Pyrogenic silicic acid, hydrophobized pyrogenic silicic acid,pyrogenic mixed oxide or pyrogenic aluminum oxide can be used asfluidizing agents.

[0015] As pyrogenic silicic acid one can use Aerosil 90, Aerosil 200,Aerosil OX 50 or Aerosil 300, as hydrophobized pyrogenic silicic acidone may use Aerosil R 8200, Aerosil R 202 or Aerosil R 972, as pyrogenicmixed oxides one can use Aerosil MOX 80 or Aerosil MOX 170, and aspyrogenic aluminum oxide one can use Aluminium oxide C (Degussa AG).

[0016] The fluidizing agent can be used in amounts of 0.1-10 wt %,preferably 0.5-2 wt %, with respect to the carbon black.

[0017] The fluidizing agent can be mixed with the carbon black in thefluidized bed or introduced into the fluidized bed in premixed form.

[0018] The post-treatment agent can be an oxidation agent or extractionagent.

[0019] Ozone or NO₂ can be used as oxidation agents.

[0020] Air, steam or air/steam mixtures can be used as extractionagents, for example, in order to reduce the extract content of carbonblacks.

[0021] The post-treatment agent can be sprayed into the fluidized bed.The post-treatment can be carried out at temperatures from 10° C. to1200° C.

[0022] If ozone is used as post-treatment agent, the temperature canpreferably be 10° C. to 100° C.

[0023] If NO₂ is used as post-treatment agent, the temperature canpreferably be 100-300° C.

[0024] If air/steam is used as post-treatment agent, the temperature canpreferably be 300° C. to 600° C.

[0025] If steam is used as post-treatment agent, the temperature canpreferably be 800-1100° C. The residence time in the fluidized bed canamount to 0.1-10 h, preferably 1-5 h. The amount of post-treatment agentcan be from 1 mg/g of carbon black up to 10 g/g of carbon black. Thepost-treatment agent can be introduced into the fluidized bed inpreheated form.

[0026] The fluidized bed can be operated continuously.

[0027] The carbon black produced with the method in accordance with theinvention can then be blown with air or nitrogen in order to removeexcess post-treatment agent. The blowing can take place in the fluidizedbed or outside the fluidized bed. The blowing times can be from 10 minto 10 h, preferably 30 min to 2 h. The blowing temperature can be 20° to300° C., preferably 50° to 200° C.

[0028] The post-treated carbon blacks produced by the method inaccordance with the invention can be used as pigment blacks.

[0029] The method in accordance with the invention has the advantagethat carbon blacks that are difficult to fluidize, for example, furnaceblacks, can be readily fluidized through the addition of fluidizingagents. Other advantages of the method in accordance with the inventionover the known stirred fixed bed are the optimum mass and energytransfer, the very good homogeneity of the post-treated carbon black,and [operation] in a reactor, which can be operated continuously andwithout mechanically moving parts.

EXAMPLES

[0030] The carbon blacks listed in Table 1 are used for the examples.TABLE 1 Printex Carbon black 30 Printex 60 Printex 90 Printex 3 IodineNo. mg/g 87 127 350 96 (ASTM 1510) CTAB m₂/g 78 102 245 83 (ASTM 3765)DBP mL/100 g 108 109 95 133 (ASTM 2414) Oil absorption g/100 g 590 600750 710 (DIN ENISO 787-5) Volatiles wt % 2.7 2.3 2.5 2.0 950° C. (DIN53552) pH (DIN 9.6 9.5 9.2 10.0 ENISO 787-9) Bulk weight g/L 155 200 8961 (DIN 53600)

[0031] Printex 30, Printex 60, Printex 90 and Printex 3 are pigmentblacks made by Degussa AG.

[0032] The pure carbon blacks can be present in the fluidized bed in anonfluidized form. The carbon blacks can remain unfluidized untilAerosil R 812 S is added. Aerosil R 812 S is mixed into the carbon blackin an amount of 1 wt %.

Example 1

[0033] The oxidation of Printex 30 with ozone and NO₂ is carried out intwo fluidized bed devices of different sizes (diameter 80 mm and 200mm). With amounts of air as are used for oxidation of gas blacks,fluidized bed conditions are achieved through the addition of Aerosil.By varying the reaction time and the amount of carbon black used, thedifferent contents of volatiles are established, where a volatilescontent of 5.0 wt % does not represent the upper limit. Theozone-oxidized carbon blacks clearly have better oil absorption than theNO₂-oxidized carbon blacks for the same degree of oxidation. The testparameters and properties of the carbon blacks are listed in Table 2.TABLE 2 Printex 30 Printex 30 Printex 30 Printex 30 Ozone- Ozone-NO₂-oxidized NO₂-oxidized oxidized oxidized Amount of g 2500 2500 25002500 carbon black Set ° C. 220 220 20 20 temperature Amount of air Nl/h1500 1500 1500 1500 Amount of Nl/h 70 70 — — NO₂ NO₂ Vol. % 4.7 4.7 — —concentration Ozone g/Nm³ — — 21 21 concentration Amount of g/h — — 31.531.5 ozone Reaction time h 0.5 2.0 2.0 6.0 Blowing time h 1 1 1 1 Iodinemg/g 77 82 54 43 number CTAB m²/g 80 88 86 94 DBP mL/100 g 108 106 111111 Oil absorption g/100 g 540 470 340 370 Volatiles wt % 2.7 5.3 3.14.5 pH 4.4 3.6 3.4 2.7 Bulk weight g/L 157 277 168 140

Example 2

[0034] The oxidation of Printex 60 with ozone is carried out in the80-mm diameter fluidized bed apparatus. By varying the reaction time andthe amount of carbon black that is used, different volatiles contentsare established. The effect of the oxone oxidation on the oilabsorption, which is clearly reduced even at low degrees of oxidation,is especially clear. The test parameters and carbon black properties arelisted in Table 3. TABLE 3 Printex 60 Printex 60 Ozone- Ozone- Printex60 oxidized oxidized Ozone-oxidized Amount of g 600 500 400 carbon blackSet temperature ° C. 20 20 20 Amount of air Nl/H 500 500 750 Ozone g/Nm³21.0 21.0 15.6 concentration Amount of ozone g/h 10.5 10.5 11.7 Reactiontime h 4.0 4.0 3.0 Blowing time h 1 1 1 Iodine number mg/g 64 50 37 CTABm²/g 113 127 129 DBP mL/100 g 115 113 114 Oil absorption g/100 g 320 234210 Volatiles wt % 3.9 5.7 6.1 pH 2.8 2.7 2.6 Bulk weight g/L 204 258244

Example 3

[0035] The oxidation of Printex 90 with ozone is carried out in twofluidized bed devices of different sizes (diameter 80 mm and 200 mm).The different volatiles contents are set by varying the reaction time,where a volatiles content of 10 wt % is possible. The test parametersand carbon black properties are listed in Table 4. TABLE 4 Printex 90Printex 90 Ozone- Ozone- Printex 90 oxidized oxidized Ozone-oxidizedAmount of g 1000 1000 1000 carbon black Set temperature ° C. 20 20 20Amount of air Nl/H 1000 1250 1000 Ozone g/Nm³ 31.6 36.0 36.0concentration Amount of ozone g/h 31.6 15.0 36.0 Reaction time h 3.0 2.56.0 Blowing time h 1 1 1 Iodine number mg/g 238 215 147 CTAB m²/g 283271 300 DBP mL/100 g 63 83 Oil absorption g/100 g 580 420 320 Volatileswt % 5.9 7.4 9.8 pH 3.1 2.9 2.3 Bulk weight g/L 102 98

Example 4

[0036] The oxidation of Printex 3 with ozone is carried out in twofluidized bed devices of different sizes (diameter 80 mm and 200 mm).Carbon blacks with volatiles contents from 3.1 to 11.5 wt % areproduced. The blowing time is 1 h, in order to remove adhering ozone orlabile peroxides on the carbon black surface. The carbon blacks are thendry pearled. The test parameters and carbon black properties are listedin Table 5. TABLE 5 Printex 3 Printex 3 Printex 3 Printex 3 Printex 3Ozone- Ozone- Ozone- Ozone- Ozone- oxidized oxidized oxidized oxidizedoxidized Amount of g 1000 1000 1500 1500 1500 carbon black Set ° C. 2020 20 20 20 temperature Amount of Nl/h 1250 650 1250 1500 1500 air Ozoneg/Nm³ 30.6 23.5 36.3 32.9 32.7 concentration Amount of g/h 38.3 15.345.4 49.4 49.1 ozone Reaction h 3.0 4.0 4.0 8.0 24.0 time Blowing h 1 11 1 1 time Iodine mg/g 79 52 63 24 22 number CTAB m²/g 98 104 122 142175 DBP mL/100 g 132 134 136 137 138 Oil g/100 g 400 310 350 190 180absorption Volatiles wt % 3.1 3.7 5.5 7.7 11.5 pH 4.1 3.2 3.0 2.5 2.3Bulk weight g/L 256 200 212 276 222

1. A method for producing post-treated carbon black, characterized bythe fact that the carbon black is fluidized in a fluidized bed with theaddition of fluidizing agents and brought into contact with apost-treatment agent.
 2. A method for producing post-treated carbonblack as in claim 1, characterized by the fact that furnace black, gasblack, channel black, flame black, thermal black, acetylene black,plasma black, inversion blacks, Si-containing blacks, metal-containingblacks, arc black and blacks that are by-products of chemical productionprocesses are used as carbon black.
 3. A method for producingpost-treated black as in claim 1, characterized by the fact that afurnace black with a DBP value greater than 70 mL/100 g is used ascarbon black.
 4. A method for producing post-treated black as in claim1, characterized by the fact that pyrogenic silicic acid, hydrophobizedpyrogenic silicic acid, pyrogenic mixed oxide or pyrogenic aluminumoxide is used as fluidizing agent.
 5. A method for producingpost-treated carbon black as in claim 1, characterized by the fact thatthe fluidizing agent is used in amounts of 0.1-10 wt % with respect tothe carbon black.
 6. A method for producing post-treated carbon black asin claim 1, characterized by the fact that an oxidation agent orextraction agent is used as post-treatment agent.
 7. A method forproducing post-treated carbon black as in claim 6, characterized by thefact that ozone or NO₂ is used as oxidation agent.
 8. A method forproducing post-treated carbon black as in claim 6, characterized by thefact that air or an air/steam mixture is used as extraction agent.
 9. Amethod for producing post-treated carbon black as in claim 1,characterized by the fact that the fluidized bed is operatedcontinuously.
 10. A method for producing post-treated carbon black as inclaim 1, characterized by the fact that the excess post-treatment agentis blown out with air or nitrogen.